React Native Image Cache on File System with Progressive Loading

Inspired by:

• wcandillon/react-native-expo-image-cache (William Candillon)
• WrathChaos/react-native-progressive-fast-image (FreakyCoder)

Features

• Cache remote images in file system with progressive loading
• Can be used with local images
• Uses react-native-file-access for file system access
• Written in Typescript
• Uses react-native-reanimated for animations
• Retry on network failure
• Supports new Architecture, both react-native-file-access and react-native-reanimated are Fabric ready.

Caution:

If you're not using react-native-reanimated version 2.x.x then use version 1.x.x of this module

If you're looking for an image library with thumbnails visit @georstat/react-native-image-gallery

Preview

iOS:

Android:

Custom Loading Image Component: (see example)

Installation

yarn:

yarn add @georstat/react-native-image-cache react-native-file-access react-native-reanimated

npm:

npm i @georstat/react-native-image-cache react-native-file-access react-native-reanimated

link native packages:

 cd ios
 pod install

**note!

For react native >= 0.65 use react-native-file-access >= 2.0.0

Usage

Put this Global config on your app entry eg. App.tsx or index.js (Required):

Note: retryDelay and maxRetries are optional, they default to 0 which means retry logic is disabled

import { CacheManager } from '@georstat/react-native-image-cache';
import { Dirs } from 'react-native-file-access';

CacheManager.config = {
  baseDir: `${Dirs.CacheDir}/images_cache/`,
  blurRadius: 15,
  cacheLimit: 0,
  maxRetries: 3 /* optional, if not provided defaults to 0 */,
  retryDelay: 3000 /* in milliseconds, optional, if not provided defaults to 0 */,
  sourceAnimationDuration: 1000,
  thumbnailAnimationDuration: 1000,
};

Custom cache key, useful for caching images from Amazon's S3 and similar services, add this (or whatever suits your needs) on CacheManager.config:

CacheManager.config = {
  // ...
  getCustomCacheKey: (source: string) => {
    // Remove params from the URL for caching images (useful for caching images from Amazons S3 bucket and etc)
    let newCacheKey = source;
    if (source.includes('?')) {
      newCacheKey = source.substring(0, source.lastIndexOf('?'));
    }
    return newCacheKey;
  },
};

cacheLimit config: (auto pruning of cached files)

If cacheLimit is set to 0 (default value) then the cache will never be auto pruned. This setting accepts a number of Bytes eg. 1024 * 1024 * 256(~256MB) and requires react-native-file-access >= 2.4.0, if you're using < 2.4.0 then leave the default value 0 (disabled).

Cache pruning flow:

1. Get all files from baseDir.
2. Sort them by lastModified, oldest first.
3. Get total size in Bytes by using reduce array method.
4. Check total size from step 3 and subtract cacheLimit value.
5. Run a while loop and keep deleting files so long as the current cache size (step 4) is larger than the size required to trigger cache pruning (cacheLimit value).
6. All steps above will run only if the image is not already cached, it runs after downloading a new image into the cache.

Pruning has been benchmarked on iOS simulator with a 5.7MB image and ~5.000 copies of it on cache without any issues. Please note that the pruning speed/performance might differ among devices. Use cacheLimit wisely and do not set a big value.

If you want to run your own tests on simulator then the cached images are stored in this location on a Mac: /Users/<your_name>/Library/Developer/CoreSimulator/Devices/<simulator_device_id>/ data/Containers/Data/Application/<application_id>/Library/Caches/images_cache, just copy and paste multiple images in there, there's no need to download them via the app.

Directory constants, choose wisely: (react-native-file-access docs)

• Dirs.CacheDir
• Dirs.DatabaseDir (Android only)
• Dirs.DocumentDir
• Dirs.LibraryDir (iOS only)
• Dirs.MainBundleDir
• Dirs.SDCardDir (Android only)
  • Prefer FileSystem.cpExternal() when possible.

Component:

import { CachedImage } from '@georstat/react-native-image-cache';

<CachedImage
  source="https://via.placeholder.com/3500x3500"
  style={{ height: 350, width: 150 }}
  thumbnailSource="https://via.placeholder.com/350x150"
/>;

Prefetch Image(s) and store them in cache:

Accepts 2 parameters:

import { CacheManager } from '@georstat/react-native-image-cache';

const url = 'https://..../image.jpg';

const urls = [
  'https://..../image.jpg',
  'https://..../image2.jpg',
  'https://..../image3.jpg',
];

CacheManager.prefetch(url); // prefetch single image

CacheManager.prefetch(urls); // prefetch mutliple images

Prefetch Image and return blob/base64:

Accepts 2 parameters:

import { CacheManager } from '@georstat/react-native-image-cache';

const url = 'https://..../image.jpg';

CacheManager.prefetchBlob(url).then(response => console.log(response)); // response is the base64 string

Clear local cache:

import { CacheManager } from '@georstat/react-native-image-cache';

await CacheManager.clearCache();

Remove single cache entry:

const uri = 'https://.../example.jpg';

await CacheManager.removeCacheEntry(uri);

Get local cache size:

await CacheManager.getCacheSize();

Check if image is cached:

await CacheManager.isImageCached(uri);

Props

CachedImage accepts the following props:

More info about React Native Accessibility

Blog Article about React Native Accessibility

Todo:

• Convert library to React Hooks
• Make baseDir configurable
• Delete single cache entry

Sponsor

This library is developed for free.

Buy us a coffee using this link:

Authors:

• Efstathios Ntonas
• George Bakogiannis
• George Kallinikos